We have investigated the interaction of lipoproteins with liposomes to form recombinant particles. A number of lipoprotein fractions (VLDL, IDL, LDL, and HDL) all disrupt liposome structure by an essentially irreversible and qualistoichometric process. In the case of HDL, the major apoprotein, A-I, recombines with dimyristoyl phsophatidyl choline vesicle 40:1 lipid-protein ot form discs approximately 100 Angstroms in diameter and Angstroms in thickness, with proteinon the rim. These structural results were obtained by a combination of neutron scattering, electron microscopy, and column chromatography. With dipalmitoyl phosphatidylcholine, A-I also forms what we term 'vesicular recombinant" particles in a process which may relate to physiological mechanisms by which proteins are assembled into membranes and lipoproteins. To study the process we have developed a technique called "phase transition release" (PTR) which is also being applied to study incorporation of tubulin into membranes. Lipoproteins were labelled with the fluorescent lipid 3,3 diotadecylindocarbocyanine for studies of interaction will cell surface lipoprotein receptors. The lipoproteins are also being labelled with NBD lipids for two-color fluorescence identification of cells in atheroscleroic plaques.